Wheeled platforms

ABSTRACT

A wheeled platform  100  is disclosed, which is characterized by high mobility and reliability, and which can be used in a wide range of applications including transport and robotic devices. The wheeled platform  100  has fore and aft body portions  130, 132 , each body portion  130, 132  having first and second sides  106, 108 . Overlapping wheels  112, 114, 116, 118  are rotatably attached to the first side  106  and overlapping wheels  120, 122, 124, 126  are rotatably attached to the second side  108 . The fore body portion  130  can be connected to the aft body portion  132  via an articulation element  133.

CROSS REFERENCE TO RELATED APPLICATIONS

This U.S. patent application is a continuation of, and claims priorityunder 35 U.S.C. §120 from U.S. patent application Ser. No. 12/023,561,filed on Jan. 31, 2008, which is a continuation of U.S. patentapplication Ser. No. 10/614,739, filed on Jul. 7, 2003 (now U.S. Pat.No. 7,363,994), which is a continuation of U.S. patent application Ser.No. 09/826,209, filed on Apr. 4, 2001 (now U.S. Pat. No. 6,662,889),which claims priority under 35 U.S.C. §119(e) to U.S. ProvisionalApplication 60/194,922, filed on Apr. 4, 2000. The disclosures of theseprior applications are considered part of the disclosure of thisapplication and are hereby incorporated herein by reference in theirentireties.

FIELD OF THE INVENTION

The present invention relates to wheeled platforms and wheeled vehiclesin general, and in particular, relates to apparatus, configurations andmethods for providing highly mobile wheeled platforms suitable for avariety of uses, including, but not limited to, robotic devices.

BACKGROUND OF THE INVENTION

The application of robotic devices and general-purpose transportplatforms has enjoyed enormous growth in recent years, across allsectors of industrial, military and consumer/household operations, for arange of tasks limited only by the imagination of those employing suchdevices. These have included such disparate applications assurveillance, bomb disposal, industrial maintenance and householdchores. In response to these demands, a number of configurations havebeen developed to provide enhanced-mobility vehicle structures that canbe used in transport and robotic device applications over rough surfacesor terrain. Representative examples of such configurations are disclosedin the following U.S. patents:

-   -   U.S. Pat. No. 6,144,180    -   U.S. Pat. No. 5,833,248    -   U.S. Pat. No. 5,742,975    -   U.S. Pat. No. 5,579,857    -   U.S. Pat. No. 5,515,934    -   U.S. Pat. No. 5,507,358    -   U.S. Pat. No. 5,323,867    -   U.S. Pat. No. 4,993,912    -   U.S. Pat. No. 4,932,491

By way of example, U.S. Pat. No. 6,144,180 discloses a robot having abody, a pair of lift arms mounted pivotally on the body, a pair of legsupport arms mounted pivotally on the lift arms, and a pair of wheeledleg assemblies mounted pivotally on each of the leg support arms. Eachof the leg support arms is rotatable to turn one of the wheeled legassemblies, which rests on the ground at the back of the other one ofthe wheeled leg assemblies, to a position in front of the other one ofthe wheeled leg assemblies, thereby moving forward the robot body. Thelift arms can be rotated upward or downward relative to the leg supportarms to lift or lower the robot body.

U.S. Pat. No. 5,833,248 purports to show a stairway ascending/descendingvehicle that can ascend or descend stair-steps having a height greaterthan the diameter of the vehicle's wheels. The vehicle has mainshaftsrotatably supported on a front portion and a rear portion of a vehiclebody, respectively. Front arm members are mounted to the frontmainshafts; rear arm members are mounted to the rear mainshaft; and thefront and rear arm members are configured to rotate with respect to themainshafts.

U.S. Pat. No. 5,742,975 discloses an articulated vehicle for scrubbingfloor surfaces defined by intersecting aisles of relatively narrowwidth. The vehicle has articulated portions that facilitate turns innarrow aisles.

U.S. Pat. Nos. 5,579,857 and 5,507,358 disclose stair-climbing vehicleshaving a body, front and rear wheels provided at the front and rear ofthe vehicle body, respectively, front and rear auxiliary wheels forlifting the front and rear wheels, respectively, by one stair-step, adriving unit for driving each wheel, a pivoting unit for pivoting thefront and rear auxiliary wheels, sensors for detecting a riser portionof stairs, and a control unit for controlling the driving unit and therotating unit in accordance with outputs of the sensors. It is claimedthat since the vehicle ascends/descends stairs by rotation of theauxiliary wheels, a corner portion of the step of stairs is not damagedwhile the vehicle goes up and down stairs.

U.S. Pat. No. 5,515,934 discloses a modular robot body assemblysegmented into five modules, symmetrically located around a horizontalcenter shaft system, enabling the robot body, front legs, and back legsto rotate about a horizontal center axis with respect to one another.

U.S. Pat. No. 5,323,867 discloses a robot transport platform adapted forlocomotion, having a base with three wheels on each side. The wheelsnear the fore and aft ends are omnidirectional in design, while theintermediate wheel (between the omnidirectional wheels) is aconventional wheel. The omnidirectional wheels have staggered rows ofspherical rollers rotatably mounted to the circumference of the wheel'shub. Torque is provided by two electric motors independently operatingthe wheels on each side, and is transferred to the wheels via a gearbox, a chain, and cogged drive belts.

U.S. Pat. No. 4,993,912 discloses a stair climbing robot having achassis with powered, opposed front wheels and two pairs of rear wheels,each pair being rotatably mounted on a beam at opposite ends thereof,and each beam being rotatably mounted on the chassis. A drive motor isprovided for driving each pair of wheels in the same direction at apredetermined rotational velocity; and a drive means is provided forsimultaneously rotating the beams at a predetermined rotational velocityand in a predetermined direction. In operation, the beams rotate forwardwhile each pair of rear wheels rotates in an opposite direction at thesame rotational velocity. Forward movement is thus powered by the frontwheels and rotating beams, while the rotational velocity of the rearwheels relative to the terrain is zero.

U.S. Pat. No. 4,932,491 describes a vehicle having auxiliary wheels thatcan be deployed to avoid overturning the vehicle when turning,traversing a slope, climbing an embankment or the like, and to right thevehicle when it is overturned.

Although the above-described devices represent advances over previousdesigns, wheeled platforms and devices such as those disclosed in theabove-listed U.S. patents have notable limitations. They are typicallyinefficient, complex, cumbersome, heavy, and poorly suited tohigh-mobility operations on rough terrain or surfaces, such astraversing steep slopes, maneuvering around obstacles, and ascending ordescending ramps or stairs.

Accordingly, there exists a need for wheeled platforms better suited tohigh-mobility, high-agility applications on rugged terrain and steeppitches. Ideally, such structures would be relatively robust, reliable,and conservative of battery or other energy sources, while providingenhanced abilities to traverse challenging terrain, and in someinstances, to ascend or descend stairs and other obstacles. It is alsodesirable that such platforms be relatively compact, but scalable byselection of components and overall dimensions to adapt to variousexpected (and unexpected) terrain requirements.

SUMMARY OF THE INVENTION

The present invention provides wheeled platforms characterized by highmobility and reliability, which are readily used in a wide range ofapplications including transport and robotic devices. The wheeledplatforms described herein can be operated on rough or steep terrain orsurfaces; can ascend and descend conventional (and non-standard) stairs,whether indoors or outdoors; and can climb steep pitches smoothly. Onstairs, the disclosed platforms can climb and descend with a minimum ofstep-induced dynamics, such as heave, pitch, and roll.

In addition, the disclosed platforms can turn-in-place (with a turningcircle coextensive with the platform), are efficient, conservative ofenergy usage, and relatively simple in construction, and thus relativelyinexpensive and lightweight.

The wheeled platforms described herein can be scaled (by componentselection and overall dimension) so as to pass through standarddoorways, crawl under standard furniture, and ensure low powerconsumption. In such embodiments, the wheeled platforms can includemotive elements (whether electric, internal combustion or other) so thatthe platforms can propel themselves on level, uneven, or hilly ground,or over thresholds; and can maneuver on level terrain or on stairs,turning or changing direction as needed or directed.

A feature of the disclosed platforms is their ability to climb stairswith a rise per step on the same order of dimension as the diameter of awheel element.

A number of overall configurations of wheeled platforms are disclosedherein. In a first configuration, a plurality of wheels are arrayed oneither side of a body or base element, with wheel diameter and wheelspacing (or axle spacing) selected to enable the platform to traverseterrain elements, including stairs.

In another configuration, the wheeled platform is equipped with anarticulated tail element that can be controlled to make selectivecontact with terrain.

In yet another configuration, the platform is articulated for relativemovement of a first, forward body portion (referred to as a “flipper”)and second, rearward body portion (referred to as a “base”) about asubstantially horizontal axis of rotation. The flipper can be controlledto make selective contact with terrain.

In each of these configurations, wheel spacing can be selected toprovide fore/aft overlap of the wheel elements; selective rocker of thewheels can be provided to facilitate turning-in-place and efficientmovement over level terrain; independent port and starboard drives canbe provided to enable maneuvers, turns, or turns-in-place; andintermediate wheel elements (in plan view) can be mounted outwardmost,to enable turning-in-place in limited spaces. In addition, deeplystudded or scalloped wheel elements can be employed at selected wheellocations, to facilitate gripping of stair-steps.

Thus, in one aspect, the invention can be embodied in a wheeledstructure in which first and second sets of wheel elements are rotatablyattached, respectively, to first and second portions of a platform orbody, wherein a portion of at least one wheel element overlaps a portionof at least one other wheel element in the same set of wheel elements.This overlap (which in one embodiment can be termed “fore/aft overlap”)can be further defined in that each wheel element has a defined radius(which need not be equal for all wheel elements), and a portion of atleast one wheel element in a set of wheel elements overlaps anotherwheel element by a predetermined fraction of the radius of the otherwheel element. In other words, the spacing between at least two wheelelement axes will be less than the sum of the respective radii of thewheel elements. In an embodiment having equal-sized overlapping wheelelements (a constraint that is not required to practice the invention)the distance between the axes of one wheel element and another wheelelement on the same side of the platform will be less than the diameterof the wheel elements. The wheeled structure thus defined can have 2, 3,4, 5 or more axles, with 4, 6, 8 or more wheel elements (or even, insome embodiments, an odd number of wheel elements).

In another aspect of the invention, at least one of the intermediatewheel elements on each side of the wheeled structure (whether there areone or more intermediate wheels per side) are displaced outwardly from alongitudinal centerline of the body by an amount greater than that ofany end wheel element. In other words, in plan view, the centermostwheel or wheels elements have a wider “track” than the end wheelelements—i.e., the port-side and starboard-side center wheels, in planview, are displaced outwardly from the body, relative to other wheels inthe respective first and second sets of wheel elements. This increasesthe stability of the wheeled platform, while enabling the platform toturn-in-place within a circle defined by the radii of the outer cornersof the platform.

It will be noted that in the following detailed description and in theclaims, the term “at least one intermediate wheel element” is used todenote one, two, three or more wheels per side (port and starboard orleft and right) that are longitudinally between “outer” or “corner”wheel elements. Similarly, the outboard or corner wheel elements cannumber four or more. In an embodiment having four wheels, selected wheelelements can be arbitrarily designated as intermediate wheel elements.As the wheeled platform of the instant invention has no single directionof travel, the designations of left and right (in the viewerperspective) or port and starboard (in the coordinate system of thepredominate direction of travel) are arbitrary and merely denoteopposite sides of the body.

In one aspect of the invention, a selected degree of rocker is provided,such that the point of contact of the centermost wheel element on eachside of the body can be lower than the respective point of contact ofthe end wheel elements. This facilitates the wheeled platform spinningor turning-in-place, thereby increasing agility. It will be understoodby one of skill in the art that while in one embodiment, rocker of thewheel arrangement permits only one or two wheel-element pairs to contacta ground plane, in an alternate embodiment, the point of contact can becoplanar for all the wheels, depending on the weighting of the platform.

In another aspect of the invention, the body of the wheeled platformincludes first and second body portions (which in one embodiment arefore and aft body portions), wherein the first body portion is connectedto the second body portion via an articulation joint. The joint can be ahinge, pivot, or flexible body portion. The axis of articulation of theelement can be substantially horizontal. The articulation elementenables one of the body portions to act as a flipper having selective(and controllable) contact with the terrain, so as to increase thestability of the vehicle when traversing rugged terrain or climbing ordescending stairs. In one embodiment, wheels are rotatably coupled tothe flipper, and the flipper can provide support to the body (or otherportion of the body) when traversing difficult or steep terrain orstairs. Angle control or motion control elements can be provided tocontrol the angle of the flipper portion relative to the body (or otherportion of the body).

In a further aspect of the invention, drive elements are provided todrive the wheel elements. In one embodiment, an independent driveelement is arranged to drive at least one respective wheel element, andcontrol elements are provided for controlling rotation of the respectivewheel elements, to enable forward or reverse platform movement, turns orturns-in-place. In one embodiment, a first set of wheel elements iscoupled to a port side of the body, a second set of wheel elements iscoupled to a starboard side of the body, and independent port-side andstarboard-side drive elements are provided to enable forward andrearward movement, turns or turns-in-place. In another aspect of theinvention, the wheel elements in selected sets (or subsets) of wheelelements (e.g., left or right, port or starboard) can be geared orotherwise mechanically coupled so that the wheels in a wheel set turn inunison.

The wheel elements utilized in connection with the invention can includea tread portion; and in turn, the tread portion can be either smooth orpatterned (e.g., with a studded or scalloped pattern). In otherembodiments, wheel elements can be smooth or patterned with studded orscalloped patterns (without a distinct or separable tread portion). Onesuch pattern thus consists of raised, spaced apart blocks. Anotherpractice of the invention utilizes scalloped wheel elements at thecorners of the platform (assuming more than 4 wheels) and smooth wheelelements for at least one of centermost wheel elements on each side.This facilitates turn-in-place, while maintaining the terrain-handlingadvantages (e.g., stair-climbing) afforded by scalloped wheel elements.

Finally, in the case of platforms useful in stair-climbing anddescending, it has been found that the selection of wheel elementdiameter, axle count and axle spacing can and should be made inaccordance with particular mathematical functions set forth hereinafter.

In alternative embodiments of the invention, fore/aft wheel elementoverlap is not utilized, but instead, wheel element diameter, wheelspacing, platform-to-wheel spatial displacement, and in one embodiment,flipper dimensions, are selected such that the platform is sufficientlyhigh to avoid contact with obstacles or terrain elements, such asstairs. In particular, the wheels in this embodiment are disposedsufficiently close together (but without overlap) such that the vehiclecan transverse stairs, rocks, thresholds or other obstacles (in someinstances, by employing a flipper element), while maintaining theplatform at a sufficient ground clearance to avoid ground/obstaclecontact.

Additional features of the invention, its nature and various advantagesare shown and described in the accompanying drawings and writtendescription. The written description and attached drawing figurespresent the invention at various levels of enabling detail, fromconceptual to specific examples of implementation. It will beappreciated by those skilled in the art that the present invention maybe practiced in connection with details that differ from the specificexamples of implementation set forth herein. By way of example, thoseskilled in the art will appreciate that the methods, systems and devicesdescribed herein can be implemented in devices, systems and methodsdiffering from those depicted or described herein, and that the examplesset forth herein are provided by way of illustration rather thanlimitation. In other instances, conventional or otherwise well-knownstructures and devices are described by way of reference to known orconventional engineering terminology.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and embodiments of the present invention are set forthin the attached drawing figures, in which:

FIG. 1A is a plan view of one configuration of wheeled platform inaccordance with the invention.

FIG. 1B is a side view of the wheeled platform of FIG. 1A, showing afirst, “flipper” portion of the platform elevated off the ground plane.

FIG. 1C is another side view of the wheeled platform of FIG. 1A, inwhich the flipper portion has been lowered to make contact with theground plane.

FIG. 2 is a front three-quarter view of a robotic device employing awheeled platform constructed in accordance with the invention.

FIG. 3 is a three-quarter view of the robotic device of FIG. 2, showingfurther detail of the wheeled platform constructed in accordance withthe invention.

FIG. 4 is a side view of the robotic device of FIG. 2.

FIG. 5 is an isometric view of the wheeled platform utilized in therobotic device of FIG. 2.

FIG. 6 is a side view of the wheeled platform utilized in the roboticdevice of FIG. 2.

FIG. 7 is a plan view of the wheeled platform utilized in the roboticdevice of FIG. 2.

FIG. 8 is a perspective view of another embodiment of a wheeled platformaccording to the invention, with a “tail” element in a retractedposition.

FIG. 9 is a perspective view of the wheeled platform of FIG. 8, with thetail element in an extended position.

FIG. 10A is a bottom view of the wheeled platform of FIG. 8.

FIG. 10B is a side view of the wheeled platform of FIG. 8, showingdetail of the drive elements.

FIG. 11A is a top view of the wheeled platform of FIG. 8, showing thetail element in a retracted position.

FIG. 11B is another side view of the wheeled platform of FIG. 8.

FIG. 11C is a rear view of the wheeled platform of FIG. 8.

FIG. 12A is a side view of another embodiment of a wheeled platform inaccordance with the invention.

FIG. 12B is a side view of the wheeled platform of FIG. 12A ascending ordescending stairs.

FIGS. 13A, B, C, D and E are outside, edge-on and perspective views,respectively, of one embodiment of a wheel element suitable for use inwheeled platforms according to the invention.

FIG. 14 is a schematic diagram of one embodiment of a wheeled platformin accordance with the invention ascending or descending stairs.

FIGS. 15A, 15B and 15C are further schematic diagrams of one embodimentof a wheeled platform in accordance with the invention ascending ordescending stairs.

DESCRIPTION OF ILLUSTRATED EMBODIMENTS Overview

The present invention, various embodiments of which are depicted in theattached drawing figures, provides highly agile wheeled platforms thatcan be used in various transport and robotic applications and operatedon rough or steep terrain or surfaces. The disclosed platforms can bescaled, by component selection and overall dimension, so as to passthrough standard doorways, crawl under standard furniture, and ensurelow power consumption. The platforms can include motive elements(whether electric, internal combustion or other) so that the platformscan propel themselves on level, uneven, or hilly ground, or overthresholds; maneuver on level terrain or on stairs, turning or changingdirection as needed or directed; and spin or turn-in-place, with aturning circle substantially coextensive with the radius of theplatform.

A number of overall configurations of wheeled platforms are disclosedherein. In a first configuration, referred to as the “flipper”embodiments, a plurality of wheels are arrayed on either side (e.g.,left/right, port/starboard) of a body or chassis element, and the bodyor chassis is articulated to permit controlled, relative movement of afirst body portion relative to a second body portion about a first axisof rotation. In one embodiment, the first body portion is referred to asa flipper and the second body portion referred to as a “base”; and thefirst axis of rotation is substantially perpendicular to a longitudinal(or fore/aft) axis of the platform. This substantially perpendicularaxis of rotation may be substantially horizontal, and the rotation orvertical movement of the flipper about that axis can be controlled by amotor or the like, so that the flipper can make selective contact withterrain and/or to control pitch, heave and other motions of the baseportion.

In another configuration, referred to herein as the “tail” embodiments,the wheeled platform is equipped with an articulated tail element thatcan be controlled to make selective contact with terrain. In the flipperand tail configurations, the wheel elements can be disposed about theplatform such with selected fore-aft overlap between adjacent wheelelements, and such that intermediate wheel elements on each side aredisplaced outward from a fore/aft axis of the platform, so as to presenta wider track at the fore/aft centerline, thus increasing stabilitywhile maintaining the ability of the platform to turn-in-place within asmall circle. In each of these configurations, wheel diameter, wheel (oraxle) spacing and other parameters can be selected to provide, wheredesirable, fore/aft overlap of the wheel elements. In addition,selective rocker of the wheels can be provided to facilitateturning-in-place and efficient movement over level terrain. Independentport and starboard drives can be provided to enable maneuvers, turns, orturns-in-place; and intermediate wheel elements (in plan view) can bemounted outwardmost, to enable turning-in-place in limited spaces. Inaddition, deeply studded or scalloped wheel elements can be employed atselected wheel locations, to facilitate gripping of stair-steps.

In yet another embodiment, the wheels elements are not overlapping, butwheel diameter and wheel spacing (or axle spacing) are selected toenable the platform to traverse terrain elements, such as stairs and thelike, with or without the use of a flipper portion.

Finally, discussion will be provided of selection criteria and stairclimbing/descending.

Flipper Embodiment

As depicted in FIGS. 1A, 1B, and 1C, one embodiment of the invention isa wheeled platform 100 in which first and second sets 102, 104 of wheelelements are rotatably attached, respectively, to first and second sides106, 108 (in this case, left and right, or port and starboard sides) ofa body or chassis 110, wherein a portion of at least one wheel element112 overlaps a portion of at least one other wheel element 114 in thesame set of wheel elements 102, 104 with the flipper portion 125 in theforward position (see FIG. 1C).

Thus, for example, in the first or port set 102 of wheel elements 112,114, 116, 1118, wheel element 114 overlaps wheel element 112; wheelelement 116 overlaps wheel element 114; and wheel element 116 overlapswheel element 118 with the flipper portion 125 in the forward position(see FIG. 1C; see also FIG. 1A). Similarly, in the second or starboardset 104 of wheel elements 120, 122, 124, 126, wheel element 122 overlapswheel element 120; wheel element 124 overlaps wheel element 122; andwheel element 124 overlaps wheel element 126 (see FIG. 1C; see also FIG.1A).

The platform 100 depicted in FIGS. 1A, 1B, and 1C is advantageouslyemployed in the iRobot commercially available from iRobot Corporation ofSomerville, Mass., various aspects of which, including first and secondsets of wheel elements 102, 104, and wheel elements 112, 114, 116, 118,120, 122, 124, and 126, are depicted in FIGS. 2-7. However, it will beunderstood that the structures described herein can be employed in awide range of other transport and robotic applications.

Referring now to FIGS. 1-7, the overlap between adjacent wheels (whichin one embodiment can be termed “fore/aft overlap”) can be furtherdefined in that each wheel element has a defined radius (which need notbe equal for all wheel elements), and a portion of at least one wheelelement in a set of wheel elements overlaps another wheel element by apredetermined fraction of the radius of the other wheel element. Inother words, the spacing between at least two wheel element axes will beless than the sum of the respective radii of the wheel elements. In anembodiment having equal-sized wheel elements (a constraint that is notrequired to practice the invention) the distance between the axes of onewheel element and another wheel element on the same side of the platformwill be less than the diameter of the wheel elements.

It will be understood that the elements used to rotatably attach thewheel elements to the body portions, which may include axles, pins,bearings, hubs and the like, may be conventional in nature, and theindividual selection of particular coupling elements is within theability of those skilled in the art.

The wheeled platform 100 thus defined can have 2, 3, 4, 5 or more“axles”, with 4, 6, 8 or more wheel elements (or even, in someembodiments, an odd number of wheel elements). The term “axle”, as usedherein, is not limited to a physical axle passing through opposite rightand left wheels, but in preferred embodiments can include an axis ofrotation of individual wheel elements, which, in some embodiments havingport/starboard symmetry, will be common to opposite left and rightwheels. It will be understood, however, that the invention can beembodied in nonsymmetrical forms, in which there will not be a common“axle” passing through both left and right wheels.

Referring again to FIGS. 1-7, it will be seen that the body 110 of thewheeled platform 100 includes fore and aft body portions 130, 132, andthe fore portion is connected to the aft portion via an articulationelement 133. This element can be a hinge, pivot, or flexible bodyportion. The axis of articulation of the element can be substantiallyperpendicular to a longitudinal axis of the platform, such that the axisof articulation is substantially horizontal. Articulation can also beprovided in a transverse direction (i.e., with an axis of rotation aboutan axis substantially parallel to a longitudinal axis of the platform).The articulation element thus enables the fore portion to act as a“flipper” having selective (and controllable) contact with the terrain,so as to increase the stability of the vehicle when traversing ruggedterrain or climbing or descending stairs.

Thus, the illustrated embodiment is an articulated, wheeled platform, inwhich the articulation can be a substantially horizontal hinge forwardof a fore/aft center of the platform. A total of eight wheels arearrayed substantially symmetrically about the plan-view centerline, andthe centerline of articulation corresponds substantially to the secondaxle line, which is defined in this embodiment by the “axle” coupled towheel elements 114, 122.

Moreover, in the embodiment depicted in FIGS. 1-7, wheels 112 and 120are rotatably coupled to the flipper, and the flipper can providesupport to the body (or other portion of the body) when traversingdifficult or steep terrain or stairs. Examples of the use of thearticulating body portions are shown in FIGS. 12B and 14-15C.Conventional angle control or motion control elements, such as electricmotors, can be provided to control the angle of the flipper portionrelative to the body as discussed in greater detail below.

In certain embodiments, the flipper is designed as to provide forincreased stability at various angles of deployment. In FIG. 3, forexample, with the flipper 125 in a stowed position, the center ofgravity of the entire device preferably should be placed as close aspossible over the center of wheel elements 116, 124. Such aconfiguration minimizes the energy needed to propel the wheeledplatform. Likewise, the flipper 125 should be weighted such that whenthe flipper 125 is deployed in a forward position (see FIG. 1C), thecenter of gravity is moved substantially forward. This allows forgreater stability over certain terrain, such as stairs and the like. Ina preferred embodiment, the batteries for the wheeled platform arearranged in the flipper 125 to allow for this movement of the center ofgravity. One of skill in the art will recognize that the need to controlthe center of gravity may or may not be necessary, depending on the sizeof the wheels and the expected use of the platform.

Increased Track of Intermediate Wheel Elements; Rocker:

Also as most clearly shown in FIGS. 1A, 3, 5 and 7, in this embodimentof the invention, at least one of the intermediate wheel elements oneach side of the wheeled structure (whether there are one or moreintermediate wheels per side) are displaced outwardly from alongitudinal centerline of the body by an amount greater than that ofany end wheel element. In other words, in plan view, the centermostwheel or wheels elements have a wider “track” than the end wheelelements, and the port-side and starboard-side intermediate wheels, inplan view, are displaced outwardly from the body, relative to otherwheels in the respective first and second sets of wheel elements. Thisincreases the stability of the wheeled platform, while enabling theplatform to turn-in-place within a circle defined by the radii of theouter corners of the platform.

It will be noted that in the following detailed description and in theclaims, the term “at least one intermediate wheel element” is used todenote one, two, three or more wheels per side (port and starboard orleft and right) that are longitudinally between “outer” or “corner”,wheel elements. Similarly, the outboard or corner wheel elements cannumber four or more. In an embodiment having four wheels, selected wheelelements can be arbitrarily designated as intermediate wheel elements.

Also as most clearly depicted in FIGS. 1B and 1C, a selected degree ofrocker is provided, such that the point of contact of at least oneintermediate wheel element on each side (in FIGS. 1A, 1B and 1C, thecenter wheel in each set of three wheels on the base portion of theplatform) can be lower than the respective point of contact of the endwheel elements. This reduces frictional losses when the platform istraversing smooth terrain and surfaces, and facilitates spinning orturning-in-place, thereby increasing agility of the platform.

Drive Elements:

In a further aspect of the embodiment shown in FIGS. 1A, 1B and 1C,drive elements are provided to drive the wheel elements and to drive theflipper element. In one embodiment, an independent drive element isarranged to drive at least one respective wheel element, and controlelements are provided for controlling rotation of the respective wheelelements, to enable forward or reverse platform movement, turns orturns-in-place. Thus, a first set of wheel elements is coupled to a portside of the body, a second set of wheel elements is coupled to astarboard side of the body, and independent port-side and starboard-sidedrive elements are provided to enable forward and rearward movement,turns or turns-in-place. The wheel elements in selected sets (orsubsets) of wheel elements (e.g., left or right, port or starboard) canbe geared or otherwise mechanically coupled so that the wheels in awheel set turn in unison.

More particularly, as shown in FIG. 1A, drive module 230 is coupled tothe first set of wheels 102; drive module 231 is coupled to the secondset of wheels 104; and drive module 134 is coupled to the flipperportion 125, to raise and lower the flipper portion 125 as required.Each module 230, 231, 134 includes a drive motor or element and acorresponding control element.

It will be understood that conventional power transmission elements,such as shafts, couplings, gears, pulleys, belts, chains, clutches andthe like, can be used as required in the illustrated embodiments, andthe individual selection of particular drive elements is within theability of those skilled in the art.

It will also be recognized that there are various choices for activatingthe propulsion and the articulation features of the disclosed platforms.The illustrated platforms have three degrees of freedom, includingport-side propulsion; starboard-side propulsion; and articulation; andthey are conveniently activated by using three independent motors.

Moreover, in the illustrated embodiments (see, e.g., FIG. 1A), one drivemodule 230 drives all port-side wheels 102 through a reduction gearboxand a spur-gear train; a second drive module 231 drives allstarboard-side wheels 104 through a second reduction gearbox andspur-gear train; and a third drive module 134 drives the articulationelement 133 through a reduction gearbox and a worm-and-worm wheel train.In the wheeled-flipper embodiment, the articulation axis is coincidentwith a wheel-and-spur gear axis (but this is not necessary to practicethe invention), so that the spur gear train can bridge the articulationaxis without any complication beyond an inconsequential interactionbetween actuation of the articulation element 133 and limited rotationof the flipper-mounted wheels 112, 120 with respect to the base-mountedwheels 114, 116, 118, 122, 124, 126.

Finally, it will be recognized that numerous variations of the disclosedstructures and drive elements are possible, including, but not limitedto the use of three motors with different reduction and transmissionarrangements, such as jackshafts and universal joints replacing the spurgear trains of the illustrated embodiments; helical gears instead ofspur gears in the gear trains; or any combination or hybrid of theabove. Also possible is the use of a motor, with or without reduction,for each wheel, as well as for the articulation action; a single motorand two clutches, with or without reduction; or two motors and oneclutch, with or without reduction.

“Tail” Embodiment

In another embodiment of the invention, depicted in FIGS. 8, 9, 10, and11, the wheeled platform 800 is equipped with an articulated “tail”element 802, pivotally coupled to a body portion 804, that can becontrolled to make selective contact with terrain. In a manner somewhatanalogous to the flipper portion of the embodiment shown in FIGS. 1-7,the tail element 802 can provide support to the body portion 804 whenthe platform 800 is traversing difficult or steep terrain or stairs.Thus, while in FIG. 8, the tail element is retracted, FIG. 9 depicts thetail element 802 in an extended position to make selective contact withterrain or surfaces. One of skill in the art will recognize that theembodiments comprising a flipper and embodiments comprising a tail arenot mutually exclusive.

Like the embodiment shown in FIGS. 1-7, platform 800 includes first andsecond sets (102, 104) of wheel elements that are rotatably attached,respectively, to port and starboard sides of body portion 804, such thatthe corner wheel elements overlap the intermediate wheel element in eachset of wheel elements. In addition, the intermediate wheel element oneach side is displaced outwardly from a centerline of the body portion804. In this way, the intermediate wheel elements are wider apart thanthe corner wheel elements, and thus present a wider track. This aspectis similar to that shown in plan view in FIG. 1A.

It will be understood that, among other things, fewer or more than 6wheels can be utilized, that the wheels may be spaced apart in anon-overlapping fashion, and that the wheels on each side may bedisposed all in a row, rather than offset (i.e., with the intermediatewheels wider apart than the corner wheels).

In the illustrated embodiment, the body portion 804 can accommodatedrive modules 806, 810 (which may include conventional batteries,electric motors, or the like) and transmission elements 812 (which mayinclude conventional gears, pulleys, belts, chains or the like). Thetail element 802 can be pivotally coupled to the body portion 804 via aconventional articulation element 814, which can be a conventionalpivot, hinge or the like. The angle and position of the tail element 802relative to the body portion 804 can be controlled by a conventional,dedicated motion control or drive element 807 (which can be an electricmotor or the like). Alternatively, the tail element 802 can be driven bya power take-off from one of the drive modules 806, 810 used to propelthe platform 800. Power is provided by a battery included in one or thedrive modules 806, 810.

Thus, the illustrated embodiment replaces the wheeled flipper of FIGS.1-7 with an articulated tail in the base's vertical fore-and-aft centerplane. In the example shown, this configuration has six (6) wheelsarrayed in a formation like that of the base of the first designconfiguration. The curved tail lying in the fore-and-aft vertical centerplane of the vehicle, and articulated about a laterally-disposedhorizontal axis that is typically at about or just aft the aft-most axleof the vehicle, is long enough to contact a step forward of the firstaxle of the vehicle, when the tail itself is articulated furthestforward with respect to the base. The articulated curved tail can beunder independent control, like the flipper of the first configuration.It may be used to contact the first step of a stairway and lift thefirst axle of the six-wheel three-axle base, off the ground or landing,and allowing it to attain the first step. Subsequently, the curvedarticulated tail may be swung all the way aft to contact the stairs aftthe vehicle, to enhance the vehicle's stability or orientation on thestairs. In a preferred embodiment, the tail 802 in its fully deployedaft position should remain at all times above the plane defined by thewheel elements to avoid interference with stairclimbing. While anarticulated tail in the described center plane may be a preferredembodiment, this embodiment of the invention can be configured with thearticulated tail in other planes or articulated about even skewed axes.

Non-Overlapping Wheels Embodiment

FIGS. 12A, 12B: In alternative embodiments of the invention, fore/aftwheel element overlap is not utilized, but instead, wheel elementdiameter, wheel spacing, platform-to-wheel spatial displacement, and inone embodiment, flipper dimensions, are selected such that the platformis sufficiently high to avoid contact with obstacles or terrainelements, such as stairs. In particular, the wheels in this embodimentare disposed sufficiently close together (but without overlap) such thatthe vehicle can transverse stairs, rocks, thresholds or other obstacles(in some instances, by employing a flipper element), while maintainingthe platform at a sufficient ground clearance to avoid ground/obstaclecontact.

Thus, for example, FIGS. 12A and 12B are schematic side views of awheeled platform 1200 in which the wheel elements are closely spaced,but without overlap. For purposes of simplicity, the present discussionand FIGS. 12A and 12B refer focus on one side (for example, the portside) 1201 of platform 1200. It will be understood, however, that thewheel elements and drive mechanisms depicted in FIGS. 12A and 12B can beduplicated, identically or non-identically, symmetrically orasymmetrically, on at least one other side (for example, the starboardside) of the wheeled platform 1200.

As shown in FIGS. 12A and 12B, the wheeled platform 1200 includes bodyor chassis portions 1202, 1204 coupled together by at least onearticulation element 1206, which may be a conventional hinge, pivot, orflexible portion, having an axis of rotation substantially perpendicularto a longitudinal axis of the wheeled platform 1200. In the illustratedembodiment, wheels 1208, 1210, 1212 are rotatably coupled to one side1201 (for example, the port side) of body portion 1204 by conventionalelements (not shown), which may be like those discussed elsewhere inthis document with respect to other embodiments of the invention. Inturn, wheels 1214, 1216, 1218 are rotatably coupled to the one side 1201of the body portion 1202.

In the example depicted, the axis of rotation of the articulationelement 1206 is substantially horizontal, so as to permit body portions1202, 1204 to move relative to one another in a substantially verticaldirection, thus increasing terrain compliance, as shown in FIG. 12B.This articulating ability of the wheeled platform 1200 may beadvantageously employed in ascending or descending pitches or stairs, asshown in FIG. 12B.

As in other embodiments discussed herein, motors or other motion-controlelements (not shown in FIGS. 12A and 12B) can be employed to control theangle of body portion 1204 relative to body portion 1202 to facilitateascending and descending, or reduce frictional losses while movingacross relatively smooth surfaces.

The diameter of the wheel elements, wheel spacing, platform-to-wheelspatial displacement, and body portion dimensions can be selected suchthat the platform is sufficiently high to avoid contact with obstaclesor terrain elements, such as stairs. In particular, the wheels in thisembodiment are disposed sufficiently close together, and wheel diameterand platform-to-wheel displacement is selected such that the platformcan transverse stairs or other obstacles, with the platform havingsufficient ground clearance to avoid contact with the nose of eachstair.

It will be understood that more than one articulation element can beused, to further segment the body or chassis of the platform 1200, andthat such articulation elements may have an axis of rotationsubstantially parallel to a longitudinal axis of the platform 1200. Inthis way, right/left or port/starboard articulation may be provided, inaddition to fore/aft articulation. In addition, more or fewer than 6wheels on each side may be utilized.

In this embodiment, the wheels on each side of the platform may bedisposed all in a row, rather than having the intermediate wheels spacedwider apart (i.e., presenting a wider track) than the corner wheels.Alternatively, it may be useful to have at least one intermediate wheelelement on each side displaced outwardly, as in the “flipper” embodimentof FIGS. 1-7 and the “tail” embodiment of FIGS. 8-11.

Patterned Wheel Elements:

The use of one or more studded, scalloped or otherwise patterned wheelelements (or, in some cases, the tread portion of such wheel elements)at certain positions around the wheeled platform has been demonstratedto be advantageous in certain applications. Examples of such wheelelements are depicted in FIGS. 13A-13E. As shown therein, wheel elements1300 that may be utilized in connection with the invention may include awheel portion 1302 having a hub 1304; and a tire portion 1306 havingsidewalls 1308, 1310, and a tread portion 1312 that can be either smoothor patterned. This pattern, in turn, may be studded, scalloped or othersome similar pattern, whether regular or irregular, symmetrical orasymmetrical. One such pattern, shown in FIGS. 13A-13E, consists ofraised, spaced apart blocks 1314. The pattern shown in FIGS. 13A-13E hasbeen demonstrated to be advantageous in platforms intended to travelfrequently over bullnosed stairs, since the concavity of the scallopportion can effectively engage the rounded (bullnoses) leading edge ofeach stair-step, increasing traction and reducing slippage.

A particular practice of the invention utilizes scalloped wheel elementsat the corners of the platform and smooth wheel elements for at leastone of intermediate wheel elements on each side. The use of smooth wheelelements at the intermediate or center positions on, for example, a6-wheeled platform, facilitates spins and turn-in-place, whilemaintaining the terrain-handling advantages (e.g., stair-climbing)afforded by scalloped wheel elements at the 4 corners.

While the use of patterned wheel elements has been shown to beadvantageous in certain applications, it will be understood that theinvention can be practiced without the use of such wheel elements.Similarly, the invention can be practiced with different forms ofwheel/tire elements, and tires (as contrasted with wheel elements) canbe omitted.

Selection Criteria for Stair-Climbing:

In the case of platforms useful in stair-climbing and descending, it hasbeen found that the selection of wheel element diameter, axle count andaxle spacing can be made with recognition of the requirements andvehicle dynamics of stair climbing and descending. FIGS. 14-15C depictvarious platform embodiments in accordance with the invention in stairascending/descending modes.

As depicted therein, in flipper embodiments, descents may beaccomplished with the platform arrayed flipper-first (“forward”), orflipper-last (“backward”). For forward descents, the flipper angle maybe controlled to prevent the platform from toppling off the landing atthe top of a flight of steps; or to smooth out the transition off thestairs onto the bottom landing, although neither operation is necessaryfor successful descents.

In typical operation on level, hilly or uneven ground, the platform andits flipper can be operated as depicted in FIGS. 1B and 15A-15C, withthe wheels of the flipper well clear of the ground. In a preferredembodiment, the center of gravity (CG) is well forward; and with theforward CG, the platform at equilibrium on flat ground rests or operateson the wheels of other axles.

The platform can address stairs in the same configuration, with theflipper raised sufficiently for the wheels of the fore axle to climbover the first step. Once the first step is attained by the first axle,the articulated flipper can be lowered to horizontal, or slightly lower,with respect to the plane of the base, and the platform can proceed upthe stairs in this configuration, approximately as shown in FIGS.15A-15C. A more active control of the flipper angle with respect to thebase can be useful for ascents of uneven steps, slippery stairs, or forsmoothness of operation, although such active control is not necessary.

CONCLUSION

The disclosed invention thus provides wheeled platforms ideally suitedto high-mobility, high-agility applications, including transport,robotic devices and the like, useful on rugged terrain, steep pitches,and stairs, whether indoors or outdoors. The structures disclosed arerobust, reliable, and conservative of battery or other energy sources,while providing enhanced abilities to traverse challenging terrain andascend or descend stairs and other obstacles. The disclosed platformscan be relatively compact, but scalable by selection of components andoverall dimensions to adapt to various expected (and unexpected) terrainrequirements.

It will be appreciated by those skilled in the art that the presentinvention may be practiced in connection with details that differ fromthe specific examples of implementation set forth herein, and can beimplemented in devices, systems and methods differing from those shown.Thus, the details set forth herein are provided by way of illustrationrather than limitation, and the invention is limited only by the scopeof the appended claims.

1. A wheeled structure comprising: a body; right and left sets offorward and rearward wheels rotatably coupled to corresponding sides ofthe body, at least one wheel of each set of wheels driven to propel thewheeled structure; a non-articulated tail element extending from a firstend pivotally coupled to the body by an articulation element andterminating at an element-free second end; and a drive module coupled tothe tail element to control the movement of the tail element between afirst, stowed position, wherein the tail element and element-free secondend of the tail element are pivoted to lay along the body, and a second,non-stowed position where the tail element can make selective contactwith a plurality of steps of a stairway; wherein the tail element isconfigured to contact a first step of the stairway and lift the firstend wheel to attain the first step.
 2. The wheeled structure of claim 1,wherein to make selective contact with a stairway, the tail element ispivotable through a continuous range of articulated positions about thearticulation element.
 3. The wheeled structure of claim 1, wherein thetail element can make selective contact with a trailing step of thestairway.
 4. The wheeled structure of claim 1, wherein the articulationelement is a hinge.
 5. The wheeled structure of claim 1, wherein thearticulation element is a pivot.
 6. The wheeled structure of claim 1,wherein the articulation element is a flexible body portion.
 7. Thewheeled structure of claim 1, wherein the tail element is straight. 8.The wheeled structure of claim 1, wherein when the tail element isarticulated furthest forward with respect to the body, the tail is longenough to contact a stairway step forward of the first end wheel.
 9. Awheeled structure comprising: a body having first and second ends; rightand left sets of forward and rearward wheels rotatably coupled tocorresponding sides of the body, at least one wheel of each set ofwheels driven to propel the wheeled structure; a non-articulated tailelement extending from a first end pivotally coupled to the body by anarticulation element and terminating at an element-free second end; anda drive module coupled to the tail element to control the movement ofthe tail element between a first, stowed position and a second,non-stowed position where the element-free second end of the tailelement can make selective contact with a plurality of steps of astairway; wherein the tail element is configured to rotate between afirst position extending below the first end of the body and a secondposition extending past the opposite, second end of the body.
 10. Thewheeled structure of claim 9, wherein to make selective contact with astairway, the tail element is pivotable through a continuous range ofarticulated positions about the articulation element.
 11. The wheeledstructure of claim 9, wherein the tail element can make selectivecontact with a trailing step of the stairway.
 12. The wheeled structureof claim 9, wherein the articulation element is a hinge.
 13. The wheeledstructure of claim 9, wherein the articulation element is a pivot. 14.The wheeled structure of claim 9, wherein the articulation element is aflexible body portion.
 15. The wheeled structure of claim 9, wherein thetail element is straight.